A Robot Stock Car

by Paul Nielsen (representing a group of 5)

Step One

Find an inexpensive radio controlled car. We had some basic requirements.
  1. The car must be of the appropriate dimensions e.g. under 30cm in length.

  2. The car must have an appropriate steering system. Ours had an independent steering mechanism that steered hard right or hard left. We didn't actually realise this when we purchased it.

  3. Inexpensive. We went looking in the sub $60 range. The car we purchased cost $40 from Tandy (Radio Shack) Electronics.

Step Two

Purchase a computer. This was our big expense - we paid $200 for our handy board unassembled. There are some up and coming devices which are less expensive. The Handy Board is good because the standard model comes with all you need for the car project i.e. 8 digital and 7 analog inputs, 4 motor outputs, a good liquid crystal display (LCD), etc. It also comes with a battery-charger-and-computer-link package and a version of 'C' (Interactive C) which can be used to program the board. It really is quite simple to use even for non 'C' programmers like me.

Handyboard (fitted within the car body)

Step Three

You will probably need to replace the steering motor of the car with a servo motor. Try and find a suitably sized replacement. We paid $25.00 for our servo motor from a hobby shop. We used some polystyrene and insulock plastic ties to secure this, we may use epoxy putty if needed.

Step Four

Underneath the front of the car

Decide on the type of sensors you require and go shopping. We initially dabbled with infra-red (IR) emitters and sensors (They cost about $1.25 for the receiver and $1.95 for the emitter). I decided to instead use simple light dependent resistors (LDRs). These were simpler to use and gave a better reading. We then had to purchase mini light bulbs to complete this set up. We also had to purchase a Hall Effect sensor to detect the magnetic strip signaling corner entries and exits on the track (Tip: Make sure you know the Hall Effect switch's pinout). [ Editor's note: Paul sported a chip-shaped burn for a few days :-) ] We also needed some bump sensors, so I purchased some micro switches. Below is a list of the equipment and components used and their cost where known.

QuantityComponentTotal Cost
1Model Car$40.00
4mini-light bulb$10
4micro switch$7.80
1Hall Effect Sensor$3.50

Other miscellaneous items included in our project.

QuantityComponentTotal Cost
8Rechargeable Batteries AA 1000 mA$40
6Rechargeable Batteries AA 600 mA$15
15 metresInsulated Wire$4.50
6HeatShrink Tubing 2.5mm/1.5mm x 1.2m$7.20
228Way Launcher Vertical$3.00
1Pkt Self Tapper Screws$2.20
1Battery Holder 6AA$1.50
1Quality 9v battery snap$0.55
1pkt insulok plastic ties$6.00
Electrical Solder

Tools we used on this project

Wire Stripper double action$7.47
Soldering Iron
Heat Glue Gun
Battery Charger
Arlec Handy Drill Kit$50
Long Nose Pliers
Stub Nose Pliers
Side Cutters
Screw Driver Set
Drill Set
Male/Female Parallel Computer Cable
OtherKneed It Epoxy Putty$12

Step 5

Stick it all together!

The construction process was simply a matter of stripping the car of its radio control gear, replacing the steering motor with the servo, drilling holes ... soldering and wiring in all the sensors. Nothing was too difficult, although a reasonable amount of time was required. We used hot glue and screws to mount the sensors. The wiring of the sensors and motors to the handy board is pretty well 'plug and play'. We simply followed instructions in the Handy Board manual which is actually relatively easy to understand. We did do it hard with the Handy Board in that we had to solder this together - we paid less ($200) for the unsoldered version. I recommend getting the finished product simply to save time and trouble. Hence I have based our costs on the $250 assembled version.

We have now completed the construction of the car and are busily programming it to win the race - we hope. What's the cost? Well it's hard to say in total because we in a team of 5 had a number of resources on hand i.e. all the non priced items. However to save you the trouble of adding up the figures, so far we have spent

The Total Cost To Date is:          $418.25

I didn't include the battery charger or wire strippers as these are non car specific. Note too the battery price is not exact as I actually paid more by not shopping around. I actually paid $6.89 for each 800mA battery. These were quality batteries, but I found the prices at Jaycar for the nameless ones much more reasonable. We used 2 sets of batteries. The 8 x 800mA batteries we placed in the cars existing battery holder. These batteries drive the cars main motor a 5volt tap drives the cars servo motor. The other 6 batteries were standard arlec I had around the house purchased at Kmart. These we used to drive the computer and lights for the LDR sensors.

If one takes out the computer and the batteries, the cost is a reasonable $113.25 for our little car. That's a $73.25 adaptation to our $40 radio controlled car.

I hope this is useful and inspires lots of people to have a go in this interesting competition.